Print prime numbers from 1 to N in reverse order | C # program to print all primes between 1 to N in reverse order using Sieve of Eratosthenes ; Create a boolean array " prime [ 0 . . n ] " and initialize all entries it as true . A value in prime [ i ] will finally be false if i is Not a prime , else true . ; If prime [ p ] is not changed , then it is a prime ; Update all multiples of p ; Print all prime numbers ; Driver code ; static input ; To display ; calling the function
using System ; class GFG { static void reverseorder ( int n ) { bool [ ] prime = new bool [ n + 1 ] ; for ( int i = 0 ; i < n ; i ++ ) prime [ i ] = true ; for ( int p = 2 ; p * p <= n ; p ++ ) { if ( prime [ p ] == true ) { for ( int i = p * 2 ; i <= n ; i += p ) prime [ i ] = false ; } } for ( int i = n ; i >= 2 ; i -- ) if ( prime [ i ] == true ) Console . Write ( i + " ▁ " ) ; } public static void Main ( ) { int N = 25 ; Console . WriteLine ( " Prime ▁ number ▁ in " + " ▁ reverse ▁ order " ) ; if ( N == 1 ) Console . WriteLine ( " No ▁ prime ▁ no " + " ▁ exist ▁ in ▁ this ▁ range " ) ; else reverseorder ( N ) ; } }